The present invention relates generally to semiconductor processing technology, and more particularly to a method for fabricating a trench capacitor.
An isolation structure is a basic structure for separating transistors and other circuit elements on an integrated circuit (IC). Shallow trench isolation (STI) and local oxidation of silicon (LOCOS) are two typical isolation structures used in ICs. An STI is formed by filling dielectric materials into a trench adjacent to a circuit element, such as a MOS transistor. A LOCOS is formed by selectively oxidizing a predetermined location in the IC. As the ICs continue to scale down, the STI becomes more popular than LOCOS, since the STI occupies less space than LOCOS, and offers better isolation performance.
Capacitors are common circuit elements in an IC. While capacitors may be conveniently constructed anywhere in the IC, there are specific locations where they can be constructed efficiently. For example, it is desirable to construct them on certain locations in order to avoid parasitic reactance. In addition, since it is costly to design new processes only for the purpose of capacitor fabrication, it is also desirable to produce them, using the processes and materials that are already involved in the fabrication of other devices in the IC.
It is therefore advantageous to construct capacitors in STI trenches that are close to one or more devices. For example, a dynamic random access memory (DRAM) cell typically involves a capacitor constructed close to a MOS transistor. While conventional methods provide techniques for constructing a capacitor in an STI trench, there are issues pertaining thereto. Specifically, conventional methods for constructing capacitors in STI trenches yield capacitors that have damaged silicon surfaces adjacent to the capacitor dielectric material. This may cause leakage current, thereby compromising the circuit performance.
Therefore, desirable in the art of semiconductor processing technology are methods for forming high quality capacitors in the STI trenches.